The present invention relates generally to a winch and associated control circuitry used to pull or lift heavy loads, and relates particularly to an electric current limiting device sensing a magnitude of current used by the winch and shutting down winch operation as a function of the magnitude of electric current drawn in conjunction with particular states of winch operation.
Winches support a wide range of applications and assume a variety of sizes and types. Winches typically have an upper load limit. Thus, a winch may be rated, for example, as a 10,000 pound winch indicating that load bearing components may withstand applied forces to a maximum 10,000 pound force.
A problem occurs when a winch is driven beyond its rating, i.e., placed under a load condition exceeding its rating. Without some form of shut-off mechanism, the weakest components of the winch can breakdown or deteriorate. Destructive failure is often the first indication that a load limit has been exceeded. Not only can this condition be costly in repair services and shutdown time, it also represents a safety hazard to those working with or in the vicinity of the winch. Even in cases where the components of the winch are designed to far exceed its load limit rating, damage may occur to supporting structures or to the item being pulled or lifted. The operator/user may simply want assurance that the load limit is not exceeded in any event. The subject matter of the present invention finds application in maintaining loads at or below a given rating.
Sensing the load condition on a given winch may be accomplished by sensing the magnitude of current delivered to the winch. U.S. Pat. No. 4,873,474, assigned in common to the assignee of the present invention, illustrates a winch with a shut-off load limiting device. Generally, the load limiting device of U.S. Pat. No. 4,873,474 senses a magnitude of current delivered to the winch and shuts off winch operation when a given magnitude is exceeded. While the load limiting device of U.S. Pat. No. 4,873,474 does allow adjustment in a threshold current used to trigger a winch shutdown, the device of U.S. Pat. No. 4,873,474 is advanced by the invention herein.